Device and method for hardening sheet metal



F. UNGERER March 5, 1957 DEVICE AND METHOD FOR HARDENING SHEET METAL Filed June 19, 195] United States Patent DEVICE AND METHGD FOR HARDENING SHEET lVIETAL Fritz Ungerer, Pforzheim, Germany, assignor to Rene van Loo, Liege, Belgium 1 This invention relates to a novel apparatus and method for hardening sheet metal of plate or band-like formation byheating and subsequent quenching.

At present when sheet metal has to.hardened,-the en tire metal sheet is first heated to hardeningteniperature and then quenched or chilled in any suitable'way. However, .experiencehas taught that this known method of hardening sheet metal frequently results in distortion, warping, buckling or bulging of the sheet metal, and that it is difficult or almost impossible to remove deformations of this kind through straightening after the tempering.

It has been found that the aforesaid deficiencies can be. practically eliminated if the material is not subjected to the heating and quenching treatment throughout its entire area at the same time, but rather if the heating and quenching treatment is applied successively to limited narrow zones of the moving sheet metal band.

The heating and quenching machinery is, therefore, designed in such a way that the sheet metal is caused to pass between burners and water nozzles in such a manner that a narrow heated zone which is directly followed by a quenching zone constantly travels along in the material, while the forward feeding or conveying of the sheet metal may be effected by means of conveyi n g rollers or clamping members. Theburners and water nozzles should be so arranged that said narrow heating and quenching zones extend across the entire width of the sheet metal perpendicular to the direction in which the material is moved through the machinery. In this way the entire area of the sheet metal can be successively subjected to the heating and subsequentquenching treatment without the risk of deformation and warping of the material.

I The invention also contemplates the provision of another heating zone behind the quenching zone in which the sheet metal is heated to tempering temperature to thereby remove inner stresses resulting from the hardening of the material.

The metal sheet is conveyed through the hardening means in slightly tensioned condition. This tensioned condition of the material can be obtained by giving the conveying rollers or conveying clamps which extract the material from the hardening means a slight advance in rotation or operation with respect to the conveying rollers or conveying clamps which feed the material into the hardening means. This advance in rotation or operation amounts to a constant angle of one revolution or to a constant portion of the path to he travelled.

The invention will be best understood from a consideration of the following detailed description, taken in connection with the accompanying drawings, forming a part of this application and in which there is illustrated by way of example two embodiments of the invention. However, the subject of the invention is not confined to any strict conformity with the showing of the drawings, but may be changed or modified, as long as such changes or modifications mark no material departure from the iice salient features of the invention as expressed in the appended claims. I

In the drawings in which like parts are referred to by the same reference numerals in all of the several figures,

Fig. 1 is a side elevation of the first form of construction provided with feed or conveying rollers and with a preliminary and final straightening machne;

Figs. 2 to 5 are diagrammatic illustrations of the second form of construction provided with clamping members, the position of the clamping members being shown at various stages of operation;

Fig. 6 is a front elevation, partly in section, of a clamp: ing member and;

Fig. 7 is a top view of a clamping member.

Referring now more particularly to the drawings, the hardening device consists of the burners 1 and 2v and of the water nozzles 3 and 4, which in both of the embodiments illustrated in the drawings are arranged above andbelow the material 5 to be hardened and are uniformly distributed in rows across the entire width of the sheet material, which is moving in the direction indicated by the arrow A, and which may either be a continuous band of sheet metal or consist of individual sheet metal plates.

Arranged behind the water nozzles 3 and 4 in the direction in which the material is moving may be additional burners 6 and '7 by means of which the material 5 is reheated, but to a lesser degree, for the purpose of tempering after the quenching.

Each of the burners 1 and 2, which heat the material up to hardening temperature, is in known manner provided with gas and air piping. The cooling liquid supplied to the nozzles 3 and 4 may be either water or oil or any other liquid suited for the quenching of sheet metal.

The forward feeding or conveying of'the material is straightening rollers 16, and a final straightening ma-' chine 15 provided with the straightening rollers .17, whereby the preliminary straightening machine and rollers 8 are arranged before the hardening.means, while the final straightening machine and rollers 9 are positioned behind the hardening device seen in the direction in which the material is fed through the several devices. In operating the device, the straightening rollers 17 of the final straightening machine 15 and the rollers 9 are given a slight advance in rotation with respect to the straightening rollers 16 of the preliminary straightening machine and the feed [rollers 8, the angle of this rotational advance being a constant one depending upon the tension at which the sheet metal band or plates are to travel between the burners 1 and 2 and the water nozzles 3 and 4. Consequently, the rollers 8, 16 and the rollers 9, 17 constitute a pair of tensioning conveyor means for tensioning, moving and straightening the sheet.

The preliminary straightening machine 14 chiefly serves the purpose of supplying the material to the burners in fairly straightened-out condition, while the final straightening after the hardening and tempering is accomplished by the straightening machine 15.

In the second form of construction illustrated in Figs. 2 to 7 the clamping members 10, 11 and 12, 13 take the place of the feed rollers 8 and 9 of the first form of construction and constitute a pair of tensioning conveyor means. These clamping members operate as follows:

At the stage of operation shown in Fig. 2, the cooperating clamping members 11 and 13 are closed, that is to sa they have seized the continuous sheet metal band or plate 5 and are conveying it at constant speed in the direction indicated by the arrow A. Before the clamping members 11 and 13 have completed this conveying operation, the clamping members 10 and 12 have reached their starting position on the left, reversed their direction of motion and after acceleration of their speed to constant conveying speed are seizing the material 5 in order to convey it for a short moment conjointly with the clamping members 11 and 13 (see Fig. 3). An instant later the clamping members 11 and 13 open up, reduce their speed and after reaching their extreme position on the right reverse their direction of motion (see Fig. 4), move back to the starting position, again reverse their direction of motion, and after acceleration to conveying speed again seize the material 5 in order to convey it for a short moment in cooperation with the clamping members 10 and 12 (see Fig. 5), whereupon the clamping members 10 and 12 open up, so that the material is then conveyed only by the clamping members 11 and 13 while the clamping members 111 and 12 are performing the return movement already described for the clamping members 11 and 13. Thus, an always constant conveying speed is reliably guaranteed. In order to make sure that also in this form of construction the material passes between the burners and nozzles; in properly tensioned condition, the clamping members 12 and 13 are given a slight advance in operation with respect to the clamping members 10 and 11, the length of that advance in operation being a constant one and depending upon the degree of tensioning required for the material in question.

From an inspection of the drawings (Figs. 6 and 7) it will be seen that the clamping members 10, 11 and 12,

13 are opened up and returned to clamping position by hydraulic means. The backward and forward movement of the clamping members may be produced in known manner either by synchronized hydraulic actuation or by mechanical means, such as cam control or the like. It is important that the material is fed forward at prefectly constant speed.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A method for hardening a metal sheet having a predetermined transversc width, comprising, in combination,

the steps of tensioning a longitudinal portion of the sheet in iongitudinal direction uniformly along the entire transverse width of the sheet; consecutively heating longitudinally adjacent narrow strip shaped zones of said portion extending through the entire transverse width of the sheet and having in longitudinal direction of said sheet an extension substantially smaller than said predetermined transverse width of the sheet; and directly after heating consecutively cooling said heated zones of said portion of the sheet so that longitudinal warping of the sheet is prevented by the small extension of the narrow stripshaped heated zone in longitudinal direction of the sheet relative to the transverse extension thereof, and by the uniform tension acting throughout the entire transverse width of said portion of the sheet.

2. Apparatus for hardening a metal sheet having a predetermined transverse width, comprising, in combination, a pair of tensioning conveyor means spaced from each other in. a conveying direction and having in a direction transverse to said conveying direction a predetermined transverse extension, said tensioning conveyor means being adapted to engage a sheet conveyed by the same along the entire transverse width of the sheet and to uniformly tension in said conveying direction and throughout the entire transverse width of the sheet the portion of the sheet located between said conveyor means; heating means located between said pair of tensioning conveyor means for heating a narrow strip shaped zone ofthe sheet having in. said transverse direction an extension substantially greater than in said conveying direction; and quenching means located directly adjacent said heating means intermediate the same and the one of said tensioning conveyor means located forwardly in said conveying direction, said quenching means having in said transverse direction an extension substantially equal to said transverse extension of said tensioning conveyor means for quenching said strip-shaped heated zones so that said portion of the sheet is heated and quenched along narrow strip-shaped zones extending throughout its entire transverse extension, and simultaneously uniformly tensioned whereby warping of the sheet is preevnted.

References Cited in the file of this patent UNITED STATES PATENTS 1,265,944 Napier May 14, 1918 1,671,810 Caughey May 29, 1928 1,732,244 Salzman Oct. 22, 1929' 2,196,902 Jones Apr. 9, 1940 2,238,667 Wales Apr. 15, 1941 2,349,569 Wilson May 23, 1944 2,367,969 Smith Jan. 23, 1945 2,401,899 Bierwirth June 11, 1946' 2,407,120 Wilson Sept. 3, 1946 2,428,825 Arnoldy Oct. 14, 1947 2,445,150 Mueller July 13, 1948 

